The present invention relates to an image reading apparatus and, particularly, to such an apparatus which can efficiently read a fluorescent image with a high SIN ratio by detecting residual fluorescence released from a fluorescent substance after the completion of irradiation with a stimulating ray.
An autoradiographic image detecting system using as a detecting material for detecting radiation a stimulable phosphor which can absorb, store and record the energy of radiation when it is irradiated by radiation and which, when it is then stimulated by an electromagnetic wave having a specified wavelength, can release stimulated emission whose light amount corresponds to the amount of radiation with which it was irradiated is known, which comprises the steps of introducing a radioactively labeled substance into an organism, using the organism or a part of the tissue of the organism as a specimen, placing the specimen and a stimulable phosphor sheet formed with a stimulable phosphor layer together in layers for a certain period of time, storing and recording radiation energy in a stimulable phosphor contained in the stimulable phosphor layer, scanning the stimulable phosphor layer with an electromagnetic wave to excite the stimulable phosphor, photoelectrically detecting the stimulated emission released from the stimulable phosphor to produce digital image signals, effecting image processing on the obtained digital image signals, and reproducing an image on displaying means such as a CRT or the like or a photographic film (see, for example, Japanese Patent Publication No. 1-60784, Japanese Patent Publication No. 1-60782, Japanese Patent Publication No. 4-3952 and the like).
There are further known an electron microscopic image detecting system and a radiographic diffraction image detecting system comprising the steps of employing, as a detecting material for an electron beam or radiation, a stimulable phosphor which can absorb and store the energy of an electron beam or radiation upon being irradiated therewith and release a stimulated emission whose amount is proportional to that of the received electron beam or radiation upon being stimulated with an electromagnetic wave having a specific wavelength range, irradiating a metal or nonmetal specimen with an electron beam and effecting elemental analysis, composition analysis or structural analysis of the specimen by detecting a diffraction image or a transmission image, or irradiating the tissue of an organism with an electron beam and detecting an image of the tissue of the organism, or irradiating a specimen with radiation, detecting a radiographic diffraction image and effecting structural analysis of the specimen (see, for example, Japanese Patent Application Laid Open No. 61-51738, Japanese Patent Application Laid Open No. 61-93538, Japanese Patent Application Laid Open No. 59-15843 and the like).
Unlike the system using a photographic film, according to these systems using the stimulable phosphor as a detecting material for an image, development, which is chemical processing, becomes unnecessary. Further, it is possible reproduce a desired image by effecting image processing on the obtained image data and effect quantitative analysis using a computer. Use of a stimulable phosphor in these processes is therefore advantageous.
On the other hand, a fluorescent image detecting system using a fluorescent substance as a labeling substance instead of a radioactively labeling substance in the autoradiographic image detecting system is known. According to this system, it is possible to study a genetic sequence, study the expression level of a gene, and to effect separation or identification of protein or estimation of the molecular weight or properties of protein or the like. For example, this system can perform a process including the steps of distributing a plurality of DNA fragments on a gel support by means of electrophoresis after a fluorescent dye was added to a solution containing a plurality of DNA fragments to be distributed, or distributing a plurality of DNA fragments on a gel support containing a fluorescent dye, or dipping a gel support on which a plurality of DNA fragments have been distributed by means of electrophoresis in a solution containing a fluorescent dye, thereby labeling the electrophoresed DNA fragments, exciting the fluorescent dye by a stimulating ray to cause it to release fluorescence, detecting the released fluorescence to produce an image and detecting the distribution of the DNA fragments on the gel support. This system can also perform a process including the steps of distributing a plurality of DNA fragments on a gel support by means of electrophoresis, denaturing the DNA fragments, transferring at least a part of the denatured DNA fragments onto a transfer support such as a nitrocellulose support by the Southern-blotting method, hybridizing a probe prepared by labeling target DNA and DNA or RNA complementary thereto with the denatured DNA fragments, thereby selectively labeling only the DNA fragments complementary to the probe DNA or probe RNA, exciting the fluorescent dye by a stimulating ray to cause it to release fluorescence, detecting the released fluorescence to produce an image and detecting the distribution of the target DNA on the transfer support. This system can further perform a process including the steps of preparing a DNA probe complementary to DNA containing a target gene labeled by a labeling substance, hybridizing it with DNA on a transfer support, combining an enzyme with the complementary DNA labeled by a labeling substance, causing the enzyme to contact a fluorescent substance, transforming the fluorescent substance to a fluorescent substance having fluorescence releasing property, exciting the thus produced fluorescent substance by a stimulating ray to release fluorescence, detecting the fluorescence to produce an image and detecting the distribution of the target DNA on the transfer support. This fluorescence detecting system is advantageous in that a genetic sequence or the like can be easily detected without using a radioactive substance.
Similarly, there is known a chemiluminescence detecting system comprising the steps of fixing a substance derived from a living body such as a protein or a nucleic acid sequence on a support, selectively labeling the substance derived from a living body with a labeling substance which generates chemiluminescent emission when it contacts a chemiluminescent substance, contacting the substance derived from a living body and selectively labeled with the labeling substance and the chemiluminescent substance, photoelectrically detecting the chemiluminescent emission in the wavelength of visible light generated by the contact of the chemiluminescent substance and the labeling substance to produce digital image signals, effecting image processing thereon, and reproducing a chemiluminescent image on a display means such as a CRT or a recording material such as a photographic film, thereby obtaining information relating to the high molecular substance such as genetic information
Since the autoradiographic image detecting system, the electron microscopic image detecting system, the radiographic diffraction image detecting system, the fluorescent image detecting system and the chemiluminescent image detecting system are used for the similar purposes, it is desirable to develop an image reading apparatus which can be used in common for all of these systems.
In fact, an image reading apparatus which can be used in common for the autoradiographic image detecting system, the chemiluminescent image detecting system, the electron microscopic image detecting system and the radiographic diffraction image detecting system using a stimulable phosphor sheet, and the fluorescent image detecting system has been already developed.
These system are constituted so as to excite a stimulable phosphor or a fluorescent substance with a stimulating ray and photoelectrically detect stimulated emission or fluorescence by a light detector, thereby producing an image. Therefore, since noise is produced if the stimulating ray is detected by the light detector, an image reading apparatus for these systems is constituted to use an optical filter to cut the stimulating ray and prevent the stimulating ray from entering the light detector.
However, since it is difficult to perfectly preventing the stimulating ray from entering the light detector, a fluorescent image detecting system has been proposed which detects residual fluorescence released from the fluorescent substance after the completion of stimulation by the stimulating ray, thereby eliminating the effect of the stimulating ray and improving the S/N ratio.
This system enables the fluorescent image detecting system to eliminate the effect of the stimulating ray and improve the S/N ratio by detecting residual fluorescence. However, a conventional image reading apparatus for the fluorescent image detecting system is often constituted to be used in common with an autoradiographic image detecting system, a chemiluminescent image detecting system, an electron microscopic image detecting system and a radiographic diffraction image detecting system using a stimulable phosphor sheet. Since the intensity of stimulated emission released from a stimulable phosphor quickly decreases after the irradiation with a stimulating ray in the autoradiographic image detecting system, the chemiluminescent image detecting system, the electron microscopic image detecting system and the radiographic diffraction image detecting system using a stimulable phosphor sheet, the image reading apparatus is constituted so as to immediately photoelectrically detect stimulated emission and fluorescence released upon stimulation. Therefore, when residual fluorescence is detected, a stimulating ray source has to be mechanically turned on and off to scan a transfer support or a gel support with a stimulating ray and residual fluorescence has to be detected during the period when the stimulating ray source is off.
However, even when the stimulating ray source is mechanically turned on and off using four vanes directly connected to a motor and rotated at 12000 r.p.m., the on-and-off cycle is on the millisecond order and when fluorescence is detected by turning on and off the stimulating ray source in accordance with such a slow cycle, it takes very long time to scan the whole surface of the transfer support or the gel support with the stimulating ray. Such a system is therefore not efficient.
It is therefore an object of the present invention to provide an image reading apparatus which can efficiently read a fluorescent image at a high S/N ratio by detecting residual fluorescence released from a fluorescent substance after the completion of irradiation with a stimulating ray.
The above and other objects of the present invention can be accomplished by an image reading apparatus comprising at least one laser stimulating ray source for emitting a laser beam, a stage on which an image carrier can be placed, a scanning mechanism for scanning the image carrier with the laser beam emitted from the at least one laser stimulating ray source, thereby stimulating the image carrier with the laser beam, a light detector for photoelectrically detecting light emitted from the image carrier, and an optical head for leading the laser beam emitted from the at least one laser stimulating ray source to the image carrier, irradiating the image carrier with the laser beam and leading light emitted from the image carrier to the light detector, the optical head being constituted so as to lead light emitted from a point of the image carrier located upstream of a point of the image carrier onto which the laser beam impinges with respect to a direction of scanning with the laser beam.
In the present invention, xe2x80x9cpoint of the image carrier located upstream of a point of the image carrier onto which the laser beam impinges with respect to a direction of scanning with the laser beamxe2x80x9d as termed here means a point on the image carrier onto which the laser beam has already impinged, regardless of whether the laser beam is moved or the image carrier is moved by the scanning mechanism. Further, xe2x80x9cresidual fluorescencexe2x80x9d as termed with respect to the present invention means fluorescence released from a fluorescent substance after completion of irradiation by a stimulating ray.
According to the present invention, since the optical head for leading the laser beam emitted from the at least one laser stimulating ray source to the light detector, irradiating the image carrier with the laser beam and leading light emitted from the image carrier to the light detector is constituted so as to lead light emitted from a point of the image carrier located upstream of the point of the image carrier onto which the laser beam impinges with respect to the direction of scanning with the laser beam, light released from the image carrier, led to the light detector by the optical head and photoelectrically detected by the light detector is light released from a portion of the image carrier which was excited by the laser beam and is no longer irradiated by the laser beam as a result of the scanning of the laser beam. Therefore, residual fluorescence can be photoelectrically detected without turning on and off the laser stimulating ray source, thereby efficiently producing a fluorescent image with a high S/N ratio.
In a preferred aspect of the present invention, the optical head further includes a stimulating ray condensing optical system for condensing a laser beam emitted from the at least one laser stimulating ray source onto the image carrier and a detected light condensing optical system disposed downstream of the stimulating ray condensing optical system with respect to the direction of the scanning with the laser beam for condensing light released from the image carrier and leading it to the light detector.
In a further preferred aspect of the present invention, the stimulating ray condensing optical system and the detected light condensing optical system are provided so that their optical axes are parallel.
In a further preferred aspect of the present invention, the stimulating ray condensing optical system and the detected light condensing optical system are provided so that their axes lie at a predetermined angle to each other.
According to this preferred aspect of the present invention, the stimulating ray condensing optical system and the detected light condensing optical system can be disposed without space constraints so that residual fluorescence can be detected shortly after completion of irradiation by the laser beam. It is therefore possible to detect a great amount of residual fluorescence, despite its being emitted only for a short period.
In a further preferred aspect of the present invention, an aperture is provided between the stimulating ray condensing optical system and the detected light condensing optical system so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough.
According to this preferred aspect of the present invention, since the aperture is provided between the stimulating ray condensing optical system and the detected light condensing optical system so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough, it is possible to cut the stimulating ray, thereby reducing noise in the image data and producing image data based on which an image having high resolution can be reproduced.
In another preferred aspect of the present invention, the optical head further comprises a first mirror for directing a laser beam emitted from at least one laser stimulating ray source to the image carrier, a condensing optical system for condensing light released from the image carrier, a second mirror whose center portion is formed so as to transmit the laser beam and which is adapted for reflecting light condensed by the condensing optical system and leading the light to the light detector and angle adjusting means for adjusting the angle of the first mirror.
According to this preferred aspect of the present invention, residual fluorescence released from a portion of the image carrier which was excited by the laser beam and as a result of the scanning of the laser beam is no longer irradiated by the laser beam can be condensed by the condensing optical system by adjusting the angle of the first mirror using the angle adjusting means so that the laser beam is impinged onto a portion of the image carrier located downstream of a portion of the image carrier facing the center of the condensing optical system with respect to the scanning direction of the laser beam and is led to the light detector by the second mirror, thereby causing the light detector to photoelectrically detect it. Therefore, a fluorescent image can be efficiently produced at a high S/N ratio by photoelectrically detecting residual fluorescence. On the other hand, a stimulable phosphor layer formed on a stimulable phosphor sheet can be stimulated with a laser beam by adjusting the angle of the first mirror using the angle adjusting means so as to direct the laser beam to the center of the condensing optical system and stimulated emission released from the stimulable phosphor layer formed on the stimulable phosphor sheet can be condensed by the condensing optical system and led to the light detector by the second mirror, thereby causing the light detector to photoelectrically detect it. Therefore, the image reading apparatus can be used in common for an autoradiographic image detecting system, a chemiluminescent image detecting system, an electron microscopic image detecting system and a radiographic diffraction image detecting system using a stimulable phosphor sheet and a fluorescent image detecting system.
In a further preferred aspect of the present invention, the second mirror is constituted as a perforated mirror whose center portion is formed with a hole.
In a further preferred aspect of the present invention, an aperture is provided between the second mirror and the light detector so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough.
According to this preferred aspect of the present invention, since the aperture is provided between the second mirror and the light detector so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough, it is possible to cut the stimulating ray, thereby reducing noise in the image data and producing image data based on which an image having high resolution can be reproduced.
In another preferred aspect of the present invention, the optical head further comprises a first mirror for directing a laser beam emitted from at least one laser stimulating ray source to the image carrier, a first condensing optical system for condensing light directed by the first mirror to the image carrier onto the image carrier, a second mirror whose center portion is located on an extension of the path of the laser beam impinging on the first mirror and which is located upstream of the first mirror with respect to the scanning direction of the laser beam and is adapted for directing the laser beam emitted from the at least one laser stimulating ray source to the image carrier, a second condensing optical system located upstream of the first condensing optical system with respect to the scanning direction of the laser beam and adapted for condensing light released from the image carrier, and a third mirror whose center portion is formed so as to transmit the laser beam and which is adapted for reflecting light condensed by the second condensing optical system and leading the light to the light detector, the second mirror being adapted for directing the laser beam emitted from the at least one laser stimulating ray source to the center portion of the third mirror and the center of the second condensing optical system, the optical system further comprising angle adjusting means for adjusting the angle of the first mirror, thereby enabling the first mirror to be selectively located in the path of the laser beam emitted from the at least one laser stimulating ray source or retracted therefrom.
According to this preferred aspect of the present invention, the laser beam emitted from the laser stimulating ray source can be led to the first condensing optical system and condensed onto the image carrier by locating the first mirror in the path of the laser beam, and light released from the image carrier can be condensed by the second condensing optical system disposed upstream of the first condensing optical system with respect to the scanning direction of the laser beam, reflected by the third mirror and led to the light detector. Therefore, since residual fluorescence released from a portion of the image carrier which was excited by the laser beam and as a result of the scanning of the laser beam is no longer irradiated by the laser beam can be led to and photoelectrically detected by the light detector, a fluorescent image can be efficiently produced at a high S/N ratio by photoelectrically detecting residual fluorescence. On the other hand, a stimulable phosphor layer formed on a stimulable phosphor sheet can be stimulated by a laser beam by adjusting the angle of the first mirror using the angle adjusting means so as to retract the first mirror from the path of the laser beam emitted from the laser stimulating ray source, lead the laser beam emitted from the laser stimulating ray source to the second mirror, cause the laser beam to pass through the center portion of the third mirror and the center of the second condensing optical system and lead the laser beam to the image carrier, and stimulated emission released from the stimulable phosphor layer formed on the stimulable phosphor sheet can be condensed by the second condensing optical system and led to the light detector by the third mirror, thereby causing the light detector to photoelectrically detect it. Therefore, the image reading apparatus can be used in common for an autoradiographic image detecting system, a chemiluminescent image detecting system, an electron microscopic image detecting system and a radiographic diffraction image detecting system using a stimulable phosphor sheet and a fluorescent image detecting system.
In a further preferred aspect of the present invention, the first condensing optical system, the first mirror, the second mirror, the third mirror and the second condensing optical system are disposed so that the optical axis of the first condensing optical system and the optical axis of the second condensing optical system are parallel to each other.
In another preferred aspect of the present invention, the first condensing optical system, the first mirror, the second mirror, the third mirror and the second condensing optical system are disposed so that the optical axis of the first condensing optical system and the optical axis of the second condensing optical system lie at a predetermined angle to each other.
According to this preferred aspect of the present invention, the first condensing optical system, the first mirror, the second mirror, the third mirror and the second condensing optical system can be disposed without space constraints so that residual fluorescence can be detected shortly period after completion of irradiation by the laser beam. It is therefore possible to detect a great amount of residual fluorescence, despite its being emitted only for a short period.
In a further preferred aspect of the present invention, the second mirror is constituted as a perforated mirror whose center portion is formed with a hole.
In a further preferred aspect of the present invention, an aperture is provided between the third mirror and the light detector so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough.
According to this preferred aspect of the present invention, since the aperture is provided between the third mirror and the light detector so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough, it is possible to cut the stimulating ray, thereby reducing noise in the image data and producing image data based on which an image having high resolution can be reproduced.
In another preferred aspect of the present invention, the optical head further comprises a first mirror for reflecting a laser beam emitted from at least one laser stimulating ray source, a condensing optical system for condensing the laser beam reflected by the first mirror onto the image carrier and condensing light released from the image carrier, and a second mirror for reflecting light released from the image carrier and condensed by the condensing optical system and leading it to the light detector, the axis of the laser beam condensed by the condensing optical system and the axis of the light released from the image carrier and condensed by the condensing optical system lying at a predetermined angle to each other.
According to this preferred aspect of the present invention, since the condensing optical system is used in common for condensing the laser beam emitted from at least one laser stimulating ray source onto the image carrier and condensing light released from the image carrier, the number of parts constituting the optical head can be reduced.
In a further preferred aspect of the present invention, an aperture is provided between the second mirror and the light detector so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough.
According to this preferred aspect of the present invention, since the aperture is provided between the second mirror and the light detector so that the center thereof coincides with the center of the path of light released from the image carrier and only light released from the image carrier and to be detected by the light detector is allowed to pass therethrough, it is possible to cut the stimulating ray, thereby reducing noise in the image data and producing image data based on which an image having high resolution can be reproduced.
The above and other objects and features of the present invention will become apparent from the following description made with reference to the accompanying drawings.